1. Field of the Invention
The invention in general relates to sonar systems, and in particular, to sonar systems utilizing a Mills Cross transducer arrangement.
2. Background Information
In a Mills Cross arrangement, two line transducers are oriented generally perpendicular to one another with one of the transducers constituting a transmitter transducer and the other a receiver transducer. The receiver apparatus is operated in a manner to form a plurality of adjacent receiver beams while the transmitter apparatus is operated such that a transmitter beam is formed which is relatively narrow in one direction and relatively wide in a transverse direction such that the transmitter beam orthogonally intersects all of the receiver beams, the intersection defining multiple adjacent target areas from which target information may be obtained.
In order to better determine the location of a target within a target area, the apparatus may be operated so as to form, for each receiver beam, a sum and difference beam pattern characterized by a single lobe sum beam in conjunction with a dual lobe difference beam with one of the lobes having a positive phase relationship and the other a negative phase relationship relative to the sum beam.
Although the sum and difference receiver beam will more narrowly define the position of a target in the target area, such target can be anywhere within a narrow strip of the target area. The present invention will eliminate any uncertainty as to the target position by precisely pinpointing the target within the target area.